This server hosts documentation but does not build it — building means running a published crate's build scripts. Upload the tree your CI already produced:
cargo doc --no-deps
tar -cf docs.tar -C target/doc .
curl -H "Authorization: $CARGO_REGISTRY_TOKEN" \
--data-binary @docs.tar -X PUT \
<base>/api/v1/crates/<name>/<version>/docsThe archive must be an uncompressed tar. Each upload replaces that version's tree.